Recent London revivals of Synge's 1907 play have tended to treat it as a dark rural tragedy. Refreshingly, John Crowley's new production, which includes a band of itinerant musicians, emphasises its roots in folk-comedy. But, although this is a perfectly creditable revival, it never achieves the right ecstatic quality.

Synge's play is part of the problem. In 1907 it caused riots at the Abbey theatre, not least because it shows how Christy Mahon achieves the status of a sex-symbol when it is assumed he has killed his father. And there is still fun to be had from Synge's comic invention and attack on the Irish propensity for myth-making: as the publican's daughter, Pegeen Mike, finally tells Christy, "There's a great gap between a gallows story and a dirty deed." But, even in its own day, Synge's play was outshone by Shaw's John Bull's Other Island, which offers a far more subversive satire on Irish role-playing. Synge's ideas have also been absorbed, and pushed to wilder extremes, by Martin McDonagh: The Lieutenant of Inishmore, especially, still angers many Irish people for its suggestion that sentimentality goes hand in hand with violence.

The real joy of Synge's play lies in its language; and that emerges only fitfully in Crowley's production. Robert Sheehan, making his stage debut as Christy, is hardly the "small, low fellow" the text suggests – more a gangling hobbledehoy transformed by his reputation for parricide. But, while Sheehan conveys Christy's spiritual change, he lacks the verbal self-intoxication and the "poet's talking" that hypnotises Pegeen. And although Ruth Negga captures both the sturdy capability and ultimate loneliness of Pegeen, even she treats the language with the caution of someone tiptoeing across a room with a precious vase.

The best performance comes from Niamh Cusack as the Widow Quin. She presents us with, instead of the customary battleaxe, a seductive predator who is a genuine rival for Christy's affections and who, when listing her accomplishments, makes "shearing a sheep" sound like a sign of sexual prowess. Kevin Trainor is also first-rate as Pegeen's supposed wooer, combining quivering cowardice with a voice that rings out like a clarion, and Scott Pask has created an excellent set consisting of a stone-walled shebeen that rotates. But, while the evening has its virtues, it will be much improved once the lead actors learn to relish the peculiar Synge-song that gives this play its life.